Absorption of Pyrimidines, Purines, and Nucleosides by Co-, Ni-, Cu-, and Fe(III)-Montmorillonite (Clay-Organic Studies XIII)

Abstract

Abstract-Absorptions of purine and pyrimidine derivatives by Co-and Ni-montmorillonite at pH < 6 and by Cu-montmorillonite at pH < 3 are similar to their absorption by Ca-montmorillonite and take place primarily by a cation exchange process. In the weakly acidic to weakly a~kaline range, absorption is due to complex formation with the inorganic cations, and decrease in the order Cu ~> Ni > Co >> Ca. Adenine, 7-methyladenine, hypoxanthine, and purine are strongly absorbed, 9-methyladenine, 6-chloropurine, and cytosine are weakly absorbed, and thymine and uracil are not absorbed. At pH < 5, the nucleosides are absorbed by Co-, Ni-, and Cu-montmorillonite in approximately the same manner as by Ca-montmorillonite, but at pH > 6 their absorptions decrease in the order Cu ~> Ni > Co > Ca. Fe(llI)-montmorillonite behaves quite differently from the other montmorillonites studied. With purines and pyrimidines, there is strong absorption from pH 3 to pH 7-8; with the nucleosides, the absorption varies considerably with the compounds considered decreasing in the order adenosine > cytidine ~> guanosine ~> inosine.INTRODUCTION THE EXPERIMENTS reported here extend those previously described on the absorption of pyrimidines, purines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite (Clay-Organic Studies, Part XII, Lailach et al., 1968) to montmorillonites saturated with the transition metal cations, Co, Ni, Cu, and Fe(llI). The previous work will be referred to as Part XII.Attention has been given mainly to the absorption isotherms in the pH range 2-12, and the organic compounds have been selected in part to show the influence of substituent groups on the complexing behavior of the compounds with the inorganic cations.The experimental methods for preparing the montmorillonites and measuring the organic absorptions are the same as those described in Part XII. Only for the alkaline samples of Fe(II1)-montmorillonite was a change made in the procedure for u.v.-spectroscopic measurements. Since under alkaline conditions a Fe(IlI)-hydroxide sol was formed which was not removed from solutions by centrifugation, a pH 2 buffer (HC1-KCI) was added to the supernatant and sedimentation of a gel took place within a few minutes. The clear supernatant solutions were then used for the spectroscopic measurements.

Adsorption of Adenine, Cytosine, Thymine, and Uracil on Sulfide-Modified Montmorillonite: FT-IR, Mössbauer and EPR Spectroscopy and X-Ray Diffractometry Studies

“…1). This adsorption order was also observed by other authors on clays (Lailach et al 1968;Lailach and Brindley 1969;Winter and Zubay 1995;Perezgasga et al 2005;Benetoli et al 2008;Hashizume et al 2010). The adsorption of adenine and cytosine on clays decreased and were statistically different (SNK test p<0.05) when the pH was higher (Fig.…”

“…In this case electrostatic force could be not used to explain the higher adsorption of these nucleic acid bases in acidic pH. According to different authors (Lailach et al 1968;Winter and Zubay 1995;Weckhuysen et al 1999;Perezgasga et al 2005;Benetoli et al 2008;Negrón-Mendoza et al 2010) the increasing adsorption of adenine/cytosine with decreasing pH is due to interaction between negatively charged clay and positively charged nucleic acid bases. Nonetheless, Hashizume and Theng (2007) observed an inverse trend for the adsorption of adenine on allophone with pHs (4.00, 6.00, 8.00).…”

“…Adenine could be available for molecular evolution, but not thymine. Using the adsorption data on clays obtained by several authors, the following ratios are described: adenine/thymine ratio range from 3.26 to 114.5 (Lailach et al 1968); adenine/thymine ratio ranging from 4.68 to 25.1 (Benetoli et al 2008). Figure 3 shows FT-IR spectra of solids nucleic acid bases adsorbed on clays in two different pHs (2.00, 7.00).…”

“…The adsorption of nucleic acid bases was studied in the following minerals: clays (Lailach et al 1968;Lailach and Brindley 1969;StrašáK 1991;Weckhuysen et al 1999;Perezgasga et al 2005;Hashizume and Theng 2007;Benetoli et al 2008;Hashizume et al 2010;Negrón-Mendoza et al 2010;Pucci et al 2010), apatite (Winter and Zubay 1995), silicon dioxide (Plekan et al 2007), graphite (Sowerby et al 2001a, b), metals sulfide compounds (Sowerby et al 1998;Bebié and Schoonen 2000;Plekan et al 2007;Hatton and Rickard 2008) and rutile (Cleaves et al 2010).…”

Adsorption of amino acids and nucleic acid bases onto minerals: a few suggestions for prebiotic chemistry experiments

“…Clays exhibit several useful properties that promote adsorption of biomolecules, including high surface area and cationic exchange capacity, catalytic properties, intercalation of molecules in mineral interlayers and global distribution. Among the clays, most of the studies of adsorption of amino acids and nucleic acid bases were performed using Na-montmorillonite (Lailach & Brindley 1969;Hedges 1977;Rishpon et al 1982;Winter & Zubay 1995;Franchi et al 2003;Parbhakar et al 2007;Benetoli et al 2008;de Santana et al 2010;Negrón-Mendoza et al 2010;Pucci et al 2010;Carneiro et al 2011a;Sciascia et al 2011) and M-(Ca, Mg, Mn, Zn, Cu, Fe, Co, Ni)-montmorillonite (Lailach et al 1968;Lailach & Brindley 1969;StrašáK 1991;Hashizume et al 2010). Other clays such as bentonite (Benetoli et al 2008), kaolinite (Hedges 1977;Rishpon et al 1982;Benetoli et al 2008), vermiculite (Fraser et al 2011a,b) and saponite (Fu et al 1996;Weckhuysen et al 1999) have also been used for adsorption experiments of amino acids and nucleic acid bases.…”